Curing of nongelling photographic emulsions



Patented Dec. 21, 1943 CURING F NONGELLING PHOTOGRAPHIC EMULSIONS Winfield Partridge, Jr., Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y.,

a corporation of New Jersey No Drawing. Application August 8, 1941,

Serial No. 406,026 I Claims. (Cl. 117-34) This invention relates to a method of curing a non-gelling photographic emulsion by subjecting a layer of the emulsion to treatment with warm air saturated with water vapor priorto drying it.

Heretolore in the making of photosensitive products the usual practice has been to coat the support with thin layer of a photographic emulsion usually of the gelling type, and to then chill it to gel the emulsion prior to dryingit. With emulsions of the non-gelling type, the chilling is ineffective and may Well be omitted.

One object of my invention is to provide a method or setting emulsions of the non-gelling type in which a more even film results than where the emulsion coating is directly subjected to drying. Other objects will appear herein.

I have found that a non-gelling photographic emulsion, the liquid portion of which is a multicornponent solvent, alter coating as a thin layer on to a support can be set by treating it with a current of warm air having a moisture content of at least 50% saturation. After setting the emulsion layer, it may be dried such as with warm dry air to form a photographic material of good evenness. v

The non-gelling emulsions are as a rule those which employ as the vehicle or carrier water susceptible cellulose derivatives with which a multi-component solvent having a large proportion of Water is used. This invention however is not limited only to the water susceptible vehicles,

as vehicles which may be developable in organic solutions could be used. The carrier for --the light-sensitive material such as silver halide salts may be far hydrolyzed cellulose acetates (or propionates or mixed esters) such as described and claimed for photographic emulsions in U. S. Patent No. 2,110,491 of Salo.

In its broadest aspects, my invention involves treatment of a non-gelling light-sensitive emul-' sion, usually in the iorm of a coating upon a supsystem appreciably, such as to near to or below the dew point of the air.

The current of air which is employed for treating the emulsion layer should be at a temperature between and 150" F. It is preferred that the temperature be at least F. due to the greater quantity or" moisture which is held by air at an elevated temperature. over the surface coated with the emulsion at the rate of 5-30 feet per second. The length of time required to cause setting of the emulsion is ordinarily 45 seconds but it may vary from at least 15 seconds up to 300 seconds depending on the various iactors'in the process.

This invention is particularly adapted to the invention is adapted to the curing of emulsion described and coatings from the emulsions claimed in Lowe and Clarke application Serial No. 402,064 filed of even date, especially containing the amount of lower aliphatic alcohol specified above. For instance an emulsion sprayed upon an aluminum surface as described in that application is satisfactorily cured by this invention.

The solvents of the non-gelling emulsions which are susceptible to curing by my invention may be 3-component such as alcohol-watercellosolve or they may have more than 3 components such as alcohol-Water-acetone-cellosolve. As pointed out in the Lowe and Clarke application there should always be preSent in these emulsions a water-miscible organic solvent having a boiling point more than C. in sufficient amount to pr event blush in the coating prepared therefrom. It is also preferable to have present in the emulsion a small proportion of a plasticizer for the cellulose ester-such as 3% of monoacetin or of one of the glycerol ethers as described in Fordyce and Salo application Serial No.,393,664, filed May 15, 1941.

The following examples illustrate m invention:

Example I A photographic emulsion consisting of silver halide dispersed in a solution of far hydrolyzed cellulose acetate (23-25% acetyl) in a mixture of 50 parts of ethyl alcohol, 50 parts of water, 15 parts of methyl cellosolve and 3 parts of monoacetin and containing small amounts of the usual emulsion addenda such as sensitizers etc. was coated on to a piece of film base at a coverage of about 30 cc. per sq. ft. of surface. A draft of air at a temperature of about F. and nearly saturated with water vapor was blown over the emulsion layer at a velocity of about 10 it. per second. The emulsion stiilcned into a smooth The air-should be passed layer and when dried in warm air gave a more even film than was obtainable by dryingsthroughout in air at room humidity.

Example II A strip of film base was coated with a photographic emulsion of the same composition as that of Example I, from an immersion hopper at 3 ft. per min. about 30 c. 6. per sq. ft. having been put on. The film was then passed into a vertical tower counter-current to a stream of air at 110 F. and nearly saturated with water vapor. The support was then passed into a section of the tower in which the relative humidity was about 50% until curing was complete.

Any film support may be employed to which the emulsion will adhere such as paper, either uncoated or with a baryta coating thereon, metals either bare or lacquered, etc., the invention residing in the curing of the emulsion layer after coating upon the support. 7

By the term non-gelling photographic emulsions is meant those emulsions which are not composed of thermal-reversible gels such as characterizes the gelatine emulsions which are usually employed for making photographic materials.

I claim: v

1. A method of setting and curing a non-gelling photographic emulsion which comprises subjecting a layer of the emulsion to treatment with air aliphatic alcohol, water and 5-30% of a watermiscible organic solvent having a boiling point above 110, the latter in sufiicient amount to prevent blush in coatings of the emulsion, which solution contains silver halide in suspension therein which comprises coating a. thin layer of the emulsion on to a supporting surface and subjecting the coating to treatment with air having a temperature of 70-150 F., a moisture saturation of at least 50% which air is moving over the layer at the rate of 5-30 feet per second prior to the drying of the emulsion layer.

4. A method of setting and curing a photographic emulsion essentially consisting of a sohaving a temperature of 70-l50 F., a moisture saturation of at least 50% which air is moving over the layer, at the rate of 5-30 feet per second, prior to the drying of theemulsion layer.

2. A method of setting and curing a non-gelling photographic emulsion which comprises subjecting a layer of the emulsion to treatment with air having a temperature of 100-150 R, a moisture saturation of at least 50% which air is moving over the layer at the rate of 5-30 feet per second, prior to the drying of the emulsion layer.

3. Afmethod of setting and curing a photographic emulsion essentially consisting of a solution of a water-susceptible cellulose ester in a solvent mixture containing 15-50% of a lower lution of a water-susceptible cellulose ester in a solvent mixture containing 15-50% of a lower aliphatic alcohol, water and 5-30% of a watermiscible organic solvent having a boiling point above 110, the latter in sufiicient amount to prevent blush in coatings of the emulsion, which solution contains silver halide in suspension therein which comprises coating a thin layer of the emulsion on to a supporting surface and subjecting the coating to treatment with air having a temperature of 100-150 F., a'moisture saturation of. at least which air is moving over the Y layer at the rate of 5-30 feet per second prior to the drying of the emulsion layer.

5. A method of curing a photographic emulsion essentially consisting of a solution of a water-susceptible cellulose acetate having an acetyl content of 23-25% in a solvent mixture containing 15-50% of a lower aliphatic alcohol, Water and 5-30% of a water-miscible organic solvent having a boiling point above 110", the latter in sufficient amount to prevent blush in coatings of the emulsion, which solution contains silver halide in suspension therein which comprises coating a thin layer of the emulsion on to a supporting surface and subjecting the coating to treatment-with air having a temperature of -150 F., a moisture saturation of at least 50% which air is moving over thelayer at the rate of 5-30 feet per second prior to the drying of the emulsion layer.

- WINFIELD PARTRIDGE, JR. 

